When the historical event of Princess Luna's banishing happened, a large entity saw the perfect time to ruin the land. It summoned a plague. A plague of demons had risen from the grounds of Equestria and swarmed the land. Killing and running down all creatures that happened to be near them as they advanced towards the great castle. Celestia's castle.

As the last form of defense before the Princess's personal Royal Guards, a battle hardened commander takes control of a massive force of soldiers. Under his guidance and encouragement, they battled to the death in an effort to repel the invading demons.

How did it all end? Well, let's just say that there wouldn't be a Ponyville if they had failed.